In countries with a high population density, such as, for example, in the Asiatic area, there are suburbs or city areas in which there are almost exclusively tall apartment blocks or high-rise buildings with up to 20 or 30 floors. These buildings are often significantly over-populated and equipped with an elevator installation having merely one elevator car. A multiplicity of persons thus has to be conveyed within the shortest possible time particularly during the peak times in morning and evening hours. During these peak times the waiting times for the elevator then easily lie within the double-figure minute range. Added to this is the fact that demands for living quality also rise in such areas. However, in most cases the construction of a further elevator shaft does not come into question for reasons of space or costs.
Measures for modernization of elevator installations are known from, for example, EP 1 319 624 A1 and EP 1 489 033 A1. In EP 1 319 624 A1 an elevator installation with two elevator cars movable in separate shafts is retrofitted with a destination call control. The destination call control also comprises several floor terminals for the input of destination call notifications or for recognition of identification codes of the user. Moreover, the destination call control comprises at least one computer unit for evaluation of the destination call notifications or for association of destination floors with recognized destination codes. In addition, a device is provided which uses a destination signal, which is output by the computer unit, in a control signal for control of the respective existing elevator control in order to move the elevator appropriate for serving a destination call. In this manner a building with several elevator shafts can be modernized in such a manner that an additional destination call control is provided so that the elevator movable in a first shaft is modernized with modern floor terminals and at the same time the second elevator movable in the other shaft is, moreover, operated conventionally with a call notification.
In the method, which is described in EP 1 489 033 A1, for modernization of an elevator installation an existing engine room in the region of the shaft head is converted into a passing space. For this purpose initially the engine room floor is removed. Car guide rails and counterweight guide rails are subsequently installed near the walls of the shaft and reach into the newly created passing space. These guide rails are constructed as a self-supporting structure and serve at the same time for supporting the drive and the electrical system. Two elevator cars are subsequently installed and are movable at the common guide rails and independently of one another in the shaft.
In this method for modernization of the elevator installation it has proved disadvantageous that extensive rebuilding measures are required, particularly the demounting of the previous guide rails, installing of new guide rails and demounting of the existing drive with subsequent reattachment of this drive.